Preheat oven to 350°F . Grease a 9x13 inch baking pan.
Combine in large bowl of electric mixer; pumpkin, cauliflower, eggs, sugars, pie spice, milk, coconut and salt.
Mix on low speed until combined and then at medium-high speed for 2 minutes. Pour mixture into prepared baking pan . Evenly spread dry cake mix over cauliflower/pumpkin mixture. Pour butter evenly over cake mix; sprinkle with pecans. Bake at 350°F for 1 hour and 15 minutes. Cool and refrigerate until ready to serve. Cut into squares and serve with whipped topping.